Last year, when we upgraded to the Axis, we were offered $43k for our 2012 Itasca Reyo. A quick search on RV trader, it looked like the going rate for those was well over $60k. So, we decided to sell it ourselves on RV Trader and a few other sites.
We went through 4 months of dealing with silly offers, "can you drive it 3 states over for us?", and flakes in general.
Then we put it on consignment where we had bought it. It took them 5 months to sell it. And, it only sold after we dropped what we would take for it by $5k. We ended up getting $47k for it.
I think part of our problem what the RV itself. It only slept 2, so that limited the demographic that would be interested in it severely.
If, or when, we upgrade from the Axis, we will take the trade in.
Remember, if you do try to sell it yourself, you have to consider your carrying costs: insurance, tag, and storage.